Originally Posted by Stiva
This is a complex question. I too am from Oz - but in the tropics and travel extensively - and I too run hot. The reality is that no suit will wear comfortably at 28 degrees and over. I have experimented with suits made in Adelaide and HK - in various fabrics.
Here are my conclusions in rough summary for what they are worth.
Super ratings have nothing to do with coolness. That rating is about the gauge of the fibre. The higher the rating, the finer the fibre and the more fibres per square inch. That has nothing to say about how tight or loose the weave is and, accordingly, how breathable/cool it wears. I avoid Supers, and particularly anything over 120s because they have a fine "hand" (ie smooth) but poor durability.
If you really want cooler you need unlined, quarter lined or half-lined, but the more scant the lining the more the suit will tend to lose its shape over time (and the more expensive it will be because the tailor will have to finish exposed seams that would otherwise be covered by lining).
Frescos have an open weave and are relatively resistant to wrinkling. Best examples : Minnis and Smiths. Weight : 8-9 oz or 9-10 oz are generally the lightest. The heavier the weight the less the wrinkling, but the hotter it wears. There is always a trade off. Light weight frescos can also be a bit see through. And they have a slightly mottled look which reduces their "conservatism".
Tropical weight wools (not frescos) can be as light as 7 oz. See Rangoons, etc. Downside: they wrinkle more and are less durable. And in my experience even they don't overcome the 28 degree problem.
Cotton is not particularly cool. It is generally tightly woven. Wrinkles. Not suitable for a conservative business office environment. Can look good in the right context though.
I also think that linen is also overrated in terms of its "coolness" - at least in the climatic sense of the word. Also wrinkles and no good for the office environment unless you have decided to unleash your Graham Greene and embrace your status as the office artiste/eccentric. But it can also look killer in the right environment and in the right colour. Stone, tan, grey, tobacco, navy - depending on skin tone and occasion. White if you are Tom Wolfe or Morgan Freeman.
Blends: I've got a 60/40 linen/wool quarter-lined airforce blue blazer suit. (See Manton thread re blazer suit.) Nice compromise on wrinkling, coolness - but still doesn't beat the 28 degree rule. Also not quite CBD.
Mills/merchants: VBC is entirely acceptable in quality. You will generally find that aficionados tend to have a favourite - but in reality there is little difference between the quality purveyors. I prefer English for largely cultural reasons. Minnis for worsted, flannel and fresco (they invented it) - and only because I have a sentimental attachment to my first pieces. Like a footy fan. But others swear by Fox, Dugdales, Harrisons, LP, W Bill, whatever.